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TOMOYO Linux Cross Reference
Linux/fs/xfs/xfs_buf.c

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  1 /*
  2  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
  3  * All Rights Reserved.
  4  *
  5  * This program is free software; you can redistribute it and/or
  6  * modify it under the terms of the GNU General Public License as
  7  * published by the Free Software Foundation.
  8  *
  9  * This program is distributed in the hope that it would be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write the Free Software Foundation,
 16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 17  */
 18 #include "xfs.h"
 19 #include <linux/stddef.h>
 20 #include <linux/errno.h>
 21 #include <linux/gfp.h>
 22 #include <linux/pagemap.h>
 23 #include <linux/init.h>
 24 #include <linux/vmalloc.h>
 25 #include <linux/bio.h>
 26 #include <linux/sysctl.h>
 27 #include <linux/proc_fs.h>
 28 #include <linux/workqueue.h>
 29 #include <linux/percpu.h>
 30 #include <linux/blkdev.h>
 31 #include <linux/hash.h>
 32 #include <linux/kthread.h>
 33 #include <linux/migrate.h>
 34 #include <linux/backing-dev.h>
 35 #include <linux/freezer.h>
 36 #include <linux/sched/mm.h>
 37 
 38 #include "xfs_format.h"
 39 #include "xfs_log_format.h"
 40 #include "xfs_trans_resv.h"
 41 #include "xfs_sb.h"
 42 #include "xfs_mount.h"
 43 #include "xfs_trace.h"
 44 #include "xfs_log.h"
 45 #include "xfs_errortag.h"
 46 #include "xfs_error.h"
 47 
 48 static kmem_zone_t *xfs_buf_zone;
 49 
 50 #ifdef XFS_BUF_LOCK_TRACKING
 51 # define XB_SET_OWNER(bp)       ((bp)->b_last_holder = current->pid)
 52 # define XB_CLEAR_OWNER(bp)     ((bp)->b_last_holder = -1)
 53 # define XB_GET_OWNER(bp)       ((bp)->b_last_holder)
 54 #else
 55 # define XB_SET_OWNER(bp)       do { } while (0)
 56 # define XB_CLEAR_OWNER(bp)     do { } while (0)
 57 # define XB_GET_OWNER(bp)       do { } while (0)
 58 #endif
 59 
 60 #define xb_to_gfp(flags) \
 61         ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
 62 
 63 
 64 static inline int
 65 xfs_buf_is_vmapped(
 66         struct xfs_buf  *bp)
 67 {
 68         /*
 69          * Return true if the buffer is vmapped.
 70          *
 71          * b_addr is null if the buffer is not mapped, but the code is clever
 72          * enough to know it doesn't have to map a single page, so the check has
 73          * to be both for b_addr and bp->b_page_count > 1.
 74          */
 75         return bp->b_addr && bp->b_page_count > 1;
 76 }
 77 
 78 static inline int
 79 xfs_buf_vmap_len(
 80         struct xfs_buf  *bp)
 81 {
 82         return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
 83 }
 84 
 85 /*
 86  * Bump the I/O in flight count on the buftarg if we haven't yet done so for
 87  * this buffer. The count is incremented once per buffer (per hold cycle)
 88  * because the corresponding decrement is deferred to buffer release. Buffers
 89  * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
 90  * tracking adds unnecessary overhead. This is used for sychronization purposes
 91  * with unmount (see xfs_wait_buftarg()), so all we really need is a count of
 92  * in-flight buffers.
 93  *
 94  * Buffers that are never released (e.g., superblock, iclog buffers) must set
 95  * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
 96  * never reaches zero and unmount hangs indefinitely.
 97  */
 98 static inline void
 99 xfs_buf_ioacct_inc(
100         struct xfs_buf  *bp)
101 {
102         if (bp->b_flags & XBF_NO_IOACCT)
103                 return;
104 
105         ASSERT(bp->b_flags & XBF_ASYNC);
106         spin_lock(&bp->b_lock);
107         if (!(bp->b_state & XFS_BSTATE_IN_FLIGHT)) {
108                 bp->b_state |= XFS_BSTATE_IN_FLIGHT;
109                 percpu_counter_inc(&bp->b_target->bt_io_count);
110         }
111         spin_unlock(&bp->b_lock);
112 }
113 
114 /*
115  * Clear the in-flight state on a buffer about to be released to the LRU or
116  * freed and unaccount from the buftarg.
117  */
118 static inline void
119 __xfs_buf_ioacct_dec(
120         struct xfs_buf  *bp)
121 {
122         lockdep_assert_held(&bp->b_lock);
123 
124         if (bp->b_state & XFS_BSTATE_IN_FLIGHT) {
125                 bp->b_state &= ~XFS_BSTATE_IN_FLIGHT;
126                 percpu_counter_dec(&bp->b_target->bt_io_count);
127         }
128 }
129 
130 static inline void
131 xfs_buf_ioacct_dec(
132         struct xfs_buf  *bp)
133 {
134         spin_lock(&bp->b_lock);
135         __xfs_buf_ioacct_dec(bp);
136         spin_unlock(&bp->b_lock);
137 }
138 
139 /*
140  * When we mark a buffer stale, we remove the buffer from the LRU and clear the
141  * b_lru_ref count so that the buffer is freed immediately when the buffer
142  * reference count falls to zero. If the buffer is already on the LRU, we need
143  * to remove the reference that LRU holds on the buffer.
144  *
145  * This prevents build-up of stale buffers on the LRU.
146  */
147 void
148 xfs_buf_stale(
149         struct xfs_buf  *bp)
150 {
151         ASSERT(xfs_buf_islocked(bp));
152 
153         bp->b_flags |= XBF_STALE;
154 
155         /*
156          * Clear the delwri status so that a delwri queue walker will not
157          * flush this buffer to disk now that it is stale. The delwri queue has
158          * a reference to the buffer, so this is safe to do.
159          */
160         bp->b_flags &= ~_XBF_DELWRI_Q;
161 
162         /*
163          * Once the buffer is marked stale and unlocked, a subsequent lookup
164          * could reset b_flags. There is no guarantee that the buffer is
165          * unaccounted (released to LRU) before that occurs. Drop in-flight
166          * status now to preserve accounting consistency.
167          */
168         spin_lock(&bp->b_lock);
169         __xfs_buf_ioacct_dec(bp);
170 
171         atomic_set(&bp->b_lru_ref, 0);
172         if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
173             (list_lru_del(&bp->b_target->bt_lru, &bp->b_lru)))
174                 atomic_dec(&bp->b_hold);
175 
176         ASSERT(atomic_read(&bp->b_hold) >= 1);
177         spin_unlock(&bp->b_lock);
178 }
179 
180 static int
181 xfs_buf_get_maps(
182         struct xfs_buf          *bp,
183         int                     map_count)
184 {
185         ASSERT(bp->b_maps == NULL);
186         bp->b_map_count = map_count;
187 
188         if (map_count == 1) {
189                 bp->b_maps = &bp->__b_map;
190                 return 0;
191         }
192 
193         bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
194                                 KM_NOFS);
195         if (!bp->b_maps)
196                 return -ENOMEM;
197         return 0;
198 }
199 
200 /*
201  *      Frees b_pages if it was allocated.
202  */
203 static void
204 xfs_buf_free_maps(
205         struct xfs_buf  *bp)
206 {
207         if (bp->b_maps != &bp->__b_map) {
208                 kmem_free(bp->b_maps);
209                 bp->b_maps = NULL;
210         }
211 }
212 
213 struct xfs_buf *
214 _xfs_buf_alloc(
215         struct xfs_buftarg      *target,
216         struct xfs_buf_map      *map,
217         int                     nmaps,
218         xfs_buf_flags_t         flags)
219 {
220         struct xfs_buf          *bp;
221         int                     error;
222         int                     i;
223 
224         bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
225         if (unlikely(!bp))
226                 return NULL;
227 
228         /*
229          * We don't want certain flags to appear in b_flags unless they are
230          * specifically set by later operations on the buffer.
231          */
232         flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
233 
234         atomic_set(&bp->b_hold, 1);
235         atomic_set(&bp->b_lru_ref, 1);
236         init_completion(&bp->b_iowait);
237         INIT_LIST_HEAD(&bp->b_lru);
238         INIT_LIST_HEAD(&bp->b_list);
239         INIT_LIST_HEAD(&bp->b_li_list);
240         sema_init(&bp->b_sema, 0); /* held, no waiters */
241         spin_lock_init(&bp->b_lock);
242         XB_SET_OWNER(bp);
243         bp->b_target = target;
244         bp->b_flags = flags;
245 
246         /*
247          * Set length and io_length to the same value initially.
248          * I/O routines should use io_length, which will be the same in
249          * most cases but may be reset (e.g. XFS recovery).
250          */
251         error = xfs_buf_get_maps(bp, nmaps);
252         if (error)  {
253                 kmem_zone_free(xfs_buf_zone, bp);
254                 return NULL;
255         }
256 
257         bp->b_bn = map[0].bm_bn;
258         bp->b_length = 0;
259         for (i = 0; i < nmaps; i++) {
260                 bp->b_maps[i].bm_bn = map[i].bm_bn;
261                 bp->b_maps[i].bm_len = map[i].bm_len;
262                 bp->b_length += map[i].bm_len;
263         }
264         bp->b_io_length = bp->b_length;
265 
266         atomic_set(&bp->b_pin_count, 0);
267         init_waitqueue_head(&bp->b_waiters);
268 
269         XFS_STATS_INC(target->bt_mount, xb_create);
270         trace_xfs_buf_init(bp, _RET_IP_);
271 
272         return bp;
273 }
274 
275 /*
276  *      Allocate a page array capable of holding a specified number
277  *      of pages, and point the page buf at it.
278  */
279 STATIC int
280 _xfs_buf_get_pages(
281         xfs_buf_t               *bp,
282         int                     page_count)
283 {
284         /* Make sure that we have a page list */
285         if (bp->b_pages == NULL) {
286                 bp->b_page_count = page_count;
287                 if (page_count <= XB_PAGES) {
288                         bp->b_pages = bp->b_page_array;
289                 } else {
290                         bp->b_pages = kmem_alloc(sizeof(struct page *) *
291                                                  page_count, KM_NOFS);
292                         if (bp->b_pages == NULL)
293                                 return -ENOMEM;
294                 }
295                 memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
296         }
297         return 0;
298 }
299 
300 /*
301  *      Frees b_pages if it was allocated.
302  */
303 STATIC void
304 _xfs_buf_free_pages(
305         xfs_buf_t       *bp)
306 {
307         if (bp->b_pages != bp->b_page_array) {
308                 kmem_free(bp->b_pages);
309                 bp->b_pages = NULL;
310         }
311 }
312 
313 /*
314  *      Releases the specified buffer.
315  *
316  *      The modification state of any associated pages is left unchanged.
317  *      The buffer must not be on any hash - use xfs_buf_rele instead for
318  *      hashed and refcounted buffers
319  */
320 void
321 xfs_buf_free(
322         xfs_buf_t               *bp)
323 {
324         trace_xfs_buf_free(bp, _RET_IP_);
325 
326         ASSERT(list_empty(&bp->b_lru));
327 
328         if (bp->b_flags & _XBF_PAGES) {
329                 uint            i;
330 
331                 if (xfs_buf_is_vmapped(bp))
332                         vm_unmap_ram(bp->b_addr - bp->b_offset,
333                                         bp->b_page_count);
334 
335                 for (i = 0; i < bp->b_page_count; i++) {
336                         struct page     *page = bp->b_pages[i];
337 
338                         __free_page(page);
339                 }
340         } else if (bp->b_flags & _XBF_KMEM)
341                 kmem_free(bp->b_addr);
342         _xfs_buf_free_pages(bp);
343         xfs_buf_free_maps(bp);
344         kmem_zone_free(xfs_buf_zone, bp);
345 }
346 
347 /*
348  * Allocates all the pages for buffer in question and builds it's page list.
349  */
350 STATIC int
351 xfs_buf_allocate_memory(
352         xfs_buf_t               *bp,
353         uint                    flags)
354 {
355         size_t                  size;
356         size_t                  nbytes, offset;
357         gfp_t                   gfp_mask = xb_to_gfp(flags);
358         unsigned short          page_count, i;
359         xfs_off_t               start, end;
360         int                     error;
361 
362         /*
363          * for buffers that are contained within a single page, just allocate
364          * the memory from the heap - there's no need for the complexity of
365          * page arrays to keep allocation down to order 0.
366          */
367         size = BBTOB(bp->b_length);
368         if (size < PAGE_SIZE) {
369                 bp->b_addr = kmem_alloc(size, KM_NOFS);
370                 if (!bp->b_addr) {
371                         /* low memory - use alloc_page loop instead */
372                         goto use_alloc_page;
373                 }
374 
375                 if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
376                     ((unsigned long)bp->b_addr & PAGE_MASK)) {
377                         /* b_addr spans two pages - use alloc_page instead */
378                         kmem_free(bp->b_addr);
379                         bp->b_addr = NULL;
380                         goto use_alloc_page;
381                 }
382                 bp->b_offset = offset_in_page(bp->b_addr);
383                 bp->b_pages = bp->b_page_array;
384                 bp->b_pages[0] = virt_to_page(bp->b_addr);
385                 bp->b_page_count = 1;
386                 bp->b_flags |= _XBF_KMEM;
387                 return 0;
388         }
389 
390 use_alloc_page:
391         start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
392         end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
393                                                                 >> PAGE_SHIFT;
394         page_count = end - start;
395         error = _xfs_buf_get_pages(bp, page_count);
396         if (unlikely(error))
397                 return error;
398 
399         offset = bp->b_offset;
400         bp->b_flags |= _XBF_PAGES;
401 
402         for (i = 0; i < bp->b_page_count; i++) {
403                 struct page     *page;
404                 uint            retries = 0;
405 retry:
406                 page = alloc_page(gfp_mask);
407                 if (unlikely(page == NULL)) {
408                         if (flags & XBF_READ_AHEAD) {
409                                 bp->b_page_count = i;
410                                 error = -ENOMEM;
411                                 goto out_free_pages;
412                         }
413 
414                         /*
415                          * This could deadlock.
416                          *
417                          * But until all the XFS lowlevel code is revamped to
418                          * handle buffer allocation failures we can't do much.
419                          */
420                         if (!(++retries % 100))
421                                 xfs_err(NULL,
422                 "%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
423                                         current->comm, current->pid,
424                                         __func__, gfp_mask);
425 
426                         XFS_STATS_INC(bp->b_target->bt_mount, xb_page_retries);
427                         congestion_wait(BLK_RW_ASYNC, HZ/50);
428                         goto retry;
429                 }
430 
431                 XFS_STATS_INC(bp->b_target->bt_mount, xb_page_found);
432 
433                 nbytes = min_t(size_t, size, PAGE_SIZE - offset);
434                 size -= nbytes;
435                 bp->b_pages[i] = page;
436                 offset = 0;
437         }
438         return 0;
439 
440 out_free_pages:
441         for (i = 0; i < bp->b_page_count; i++)
442                 __free_page(bp->b_pages[i]);
443         bp->b_flags &= ~_XBF_PAGES;
444         return error;
445 }
446 
447 /*
448  *      Map buffer into kernel address-space if necessary.
449  */
450 STATIC int
451 _xfs_buf_map_pages(
452         xfs_buf_t               *bp,
453         uint                    flags)
454 {
455         ASSERT(bp->b_flags & _XBF_PAGES);
456         if (bp->b_page_count == 1) {
457                 /* A single page buffer is always mappable */
458                 bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
459         } else if (flags & XBF_UNMAPPED) {
460                 bp->b_addr = NULL;
461         } else {
462                 int retried = 0;
463                 unsigned nofs_flag;
464 
465                 /*
466                  * vm_map_ram() will allocate auxillary structures (e.g.
467                  * pagetables) with GFP_KERNEL, yet we are likely to be under
468                  * GFP_NOFS context here. Hence we need to tell memory reclaim
469                  * that we are in such a context via PF_MEMALLOC_NOFS to prevent
470                  * memory reclaim re-entering the filesystem here and
471                  * potentially deadlocking.
472                  */
473                 nofs_flag = memalloc_nofs_save();
474                 do {
475                         bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
476                                                 -1, PAGE_KERNEL);
477                         if (bp->b_addr)
478                                 break;
479                         vm_unmap_aliases();
480                 } while (retried++ <= 1);
481                 memalloc_nofs_restore(nofs_flag);
482 
483                 if (!bp->b_addr)
484                         return -ENOMEM;
485                 bp->b_addr += bp->b_offset;
486         }
487 
488         return 0;
489 }
490 
491 /*
492  *      Finding and Reading Buffers
493  */
494 static int
495 _xfs_buf_obj_cmp(
496         struct rhashtable_compare_arg   *arg,
497         const void                      *obj)
498 {
499         const struct xfs_buf_map        *map = arg->key;
500         const struct xfs_buf            *bp = obj;
501 
502         /*
503          * The key hashing in the lookup path depends on the key being the
504          * first element of the compare_arg, make sure to assert this.
505          */
506         BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
507 
508         if (bp->b_bn != map->bm_bn)
509                 return 1;
510 
511         if (unlikely(bp->b_length != map->bm_len)) {
512                 /*
513                  * found a block number match. If the range doesn't
514                  * match, the only way this is allowed is if the buffer
515                  * in the cache is stale and the transaction that made
516                  * it stale has not yet committed. i.e. we are
517                  * reallocating a busy extent. Skip this buffer and
518                  * continue searching for an exact match.
519                  */
520                 ASSERT(bp->b_flags & XBF_STALE);
521                 return 1;
522         }
523         return 0;
524 }
525 
526 static const struct rhashtable_params xfs_buf_hash_params = {
527         .min_size               = 32,   /* empty AGs have minimal footprint */
528         .nelem_hint             = 16,
529         .key_len                = sizeof(xfs_daddr_t),
530         .key_offset             = offsetof(struct xfs_buf, b_bn),
531         .head_offset            = offsetof(struct xfs_buf, b_rhash_head),
532         .automatic_shrinking    = true,
533         .obj_cmpfn              = _xfs_buf_obj_cmp,
534 };
535 
536 int
537 xfs_buf_hash_init(
538         struct xfs_perag        *pag)
539 {
540         spin_lock_init(&pag->pag_buf_lock);
541         return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
542 }
543 
544 void
545 xfs_buf_hash_destroy(
546         struct xfs_perag        *pag)
547 {
548         rhashtable_destroy(&pag->pag_buf_hash);
549 }
550 
551 /*
552  *      Look up, and creates if absent, a lockable buffer for
553  *      a given range of an inode.  The buffer is returned
554  *      locked. No I/O is implied by this call.
555  */
556 xfs_buf_t *
557 _xfs_buf_find(
558         struct xfs_buftarg      *btp,
559         struct xfs_buf_map      *map,
560         int                     nmaps,
561         xfs_buf_flags_t         flags,
562         xfs_buf_t               *new_bp)
563 {
564         struct xfs_perag        *pag;
565         xfs_buf_t               *bp;
566         struct xfs_buf_map      cmap = { .bm_bn = map[0].bm_bn };
567         xfs_daddr_t             eofs;
568         int                     i;
569 
570         for (i = 0; i < nmaps; i++)
571                 cmap.bm_len += map[i].bm_len;
572 
573         /* Check for IOs smaller than the sector size / not sector aligned */
574         ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
575         ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
576 
577         /*
578          * Corrupted block numbers can get through to here, unfortunately, so we
579          * have to check that the buffer falls within the filesystem bounds.
580          */
581         eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
582         if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
583                 /*
584                  * XXX (dgc): we should really be returning -EFSCORRUPTED here,
585                  * but none of the higher level infrastructure supports
586                  * returning a specific error on buffer lookup failures.
587                  */
588                 xfs_alert(btp->bt_mount,
589                           "%s: daddr 0x%llx out of range, EOFS 0x%llx",
590                           __func__, cmap.bm_bn, eofs);
591                 WARN_ON(1);
592                 return NULL;
593         }
594 
595         pag = xfs_perag_get(btp->bt_mount,
596                             xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
597 
598         spin_lock(&pag->pag_buf_lock);
599         bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
600                                     xfs_buf_hash_params);
601         if (bp) {
602                 atomic_inc(&bp->b_hold);
603                 goto found;
604         }
605 
606         /* No match found */
607         if (new_bp) {
608                 /* the buffer keeps the perag reference until it is freed */
609                 new_bp->b_pag = pag;
610                 rhashtable_insert_fast(&pag->pag_buf_hash,
611                                        &new_bp->b_rhash_head,
612                                        xfs_buf_hash_params);
613                 spin_unlock(&pag->pag_buf_lock);
614         } else {
615                 XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
616                 spin_unlock(&pag->pag_buf_lock);
617                 xfs_perag_put(pag);
618         }
619         return new_bp;
620 
621 found:
622         spin_unlock(&pag->pag_buf_lock);
623         xfs_perag_put(pag);
624 
625         if (!xfs_buf_trylock(bp)) {
626                 if (flags & XBF_TRYLOCK) {
627                         xfs_buf_rele(bp);
628                         XFS_STATS_INC(btp->bt_mount, xb_busy_locked);
629                         return NULL;
630                 }
631                 xfs_buf_lock(bp);
632                 XFS_STATS_INC(btp->bt_mount, xb_get_locked_waited);
633         }
634 
635         /*
636          * if the buffer is stale, clear all the external state associated with
637          * it. We need to keep flags such as how we allocated the buffer memory
638          * intact here.
639          */
640         if (bp->b_flags & XBF_STALE) {
641                 ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
642                 ASSERT(bp->b_iodone == NULL);
643                 bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
644                 bp->b_ops = NULL;
645         }
646 
647         trace_xfs_buf_find(bp, flags, _RET_IP_);
648         XFS_STATS_INC(btp->bt_mount, xb_get_locked);
649         return bp;
650 }
651 
652 /*
653  * Assembles a buffer covering the specified range. The code is optimised for
654  * cache hits, as metadata intensive workloads will see 3 orders of magnitude
655  * more hits than misses.
656  */
657 struct xfs_buf *
658 xfs_buf_get_map(
659         struct xfs_buftarg      *target,
660         struct xfs_buf_map      *map,
661         int                     nmaps,
662         xfs_buf_flags_t         flags)
663 {
664         struct xfs_buf          *bp;
665         struct xfs_buf          *new_bp;
666         int                     error = 0;
667 
668         bp = _xfs_buf_find(target, map, nmaps, flags, NULL);
669         if (likely(bp))
670                 goto found;
671 
672         new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
673         if (unlikely(!new_bp))
674                 return NULL;
675 
676         error = xfs_buf_allocate_memory(new_bp, flags);
677         if (error) {
678                 xfs_buf_free(new_bp);
679                 return NULL;
680         }
681 
682         bp = _xfs_buf_find(target, map, nmaps, flags, new_bp);
683         if (!bp) {
684                 xfs_buf_free(new_bp);
685                 return NULL;
686         }
687 
688         if (bp != new_bp)
689                 xfs_buf_free(new_bp);
690 
691 found:
692         if (!bp->b_addr) {
693                 error = _xfs_buf_map_pages(bp, flags);
694                 if (unlikely(error)) {
695                         xfs_warn(target->bt_mount,
696                                 "%s: failed to map pagesn", __func__);
697                         xfs_buf_relse(bp);
698                         return NULL;
699                 }
700         }
701 
702         /*
703          * Clear b_error if this is a lookup from a caller that doesn't expect
704          * valid data to be found in the buffer.
705          */
706         if (!(flags & XBF_READ))
707                 xfs_buf_ioerror(bp, 0);
708 
709         XFS_STATS_INC(target->bt_mount, xb_get);
710         trace_xfs_buf_get(bp, flags, _RET_IP_);
711         return bp;
712 }
713 
714 STATIC int
715 _xfs_buf_read(
716         xfs_buf_t               *bp,
717         xfs_buf_flags_t         flags)
718 {
719         ASSERT(!(flags & XBF_WRITE));
720         ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
721 
722         bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
723         bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
724 
725         if (flags & XBF_ASYNC) {
726                 xfs_buf_submit(bp);
727                 return 0;
728         }
729         return xfs_buf_submit_wait(bp);
730 }
731 
732 xfs_buf_t *
733 xfs_buf_read_map(
734         struct xfs_buftarg      *target,
735         struct xfs_buf_map      *map,
736         int                     nmaps,
737         xfs_buf_flags_t         flags,
738         const struct xfs_buf_ops *ops)
739 {
740         struct xfs_buf          *bp;
741 
742         flags |= XBF_READ;
743 
744         bp = xfs_buf_get_map(target, map, nmaps, flags);
745         if (bp) {
746                 trace_xfs_buf_read(bp, flags, _RET_IP_);
747 
748                 if (!(bp->b_flags & XBF_DONE)) {
749                         XFS_STATS_INC(target->bt_mount, xb_get_read);
750                         bp->b_ops = ops;
751                         _xfs_buf_read(bp, flags);
752                 } else if (flags & XBF_ASYNC) {
753                         /*
754                          * Read ahead call which is already satisfied,
755                          * drop the buffer
756                          */
757                         xfs_buf_relse(bp);
758                         return NULL;
759                 } else {
760                         /* We do not want read in the flags */
761                         bp->b_flags &= ~XBF_READ;
762                 }
763         }
764 
765         return bp;
766 }
767 
768 /*
769  *      If we are not low on memory then do the readahead in a deadlock
770  *      safe manner.
771  */
772 void
773 xfs_buf_readahead_map(
774         struct xfs_buftarg      *target,
775         struct xfs_buf_map      *map,
776         int                     nmaps,
777         const struct xfs_buf_ops *ops)
778 {
779         if (bdi_read_congested(target->bt_bdev->bd_bdi))
780                 return;
781 
782         xfs_buf_read_map(target, map, nmaps,
783                      XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
784 }
785 
786 /*
787  * Read an uncached buffer from disk. Allocates and returns a locked
788  * buffer containing the disk contents or nothing.
789  */
790 int
791 xfs_buf_read_uncached(
792         struct xfs_buftarg      *target,
793         xfs_daddr_t             daddr,
794         size_t                  numblks,
795         int                     flags,
796         struct xfs_buf          **bpp,
797         const struct xfs_buf_ops *ops)
798 {
799         struct xfs_buf          *bp;
800 
801         *bpp = NULL;
802 
803         bp = xfs_buf_get_uncached(target, numblks, flags);
804         if (!bp)
805                 return -ENOMEM;
806 
807         /* set up the buffer for a read IO */
808         ASSERT(bp->b_map_count == 1);
809         bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
810         bp->b_maps[0].bm_bn = daddr;
811         bp->b_flags |= XBF_READ;
812         bp->b_ops = ops;
813 
814         xfs_buf_submit_wait(bp);
815         if (bp->b_error) {
816                 int     error = bp->b_error;
817                 xfs_buf_relse(bp);
818                 return error;
819         }
820 
821         *bpp = bp;
822         return 0;
823 }
824 
825 /*
826  * Return a buffer allocated as an empty buffer and associated to external
827  * memory via xfs_buf_associate_memory() back to it's empty state.
828  */
829 void
830 xfs_buf_set_empty(
831         struct xfs_buf          *bp,
832         size_t                  numblks)
833 {
834         if (bp->b_pages)
835                 _xfs_buf_free_pages(bp);
836 
837         bp->b_pages = NULL;
838         bp->b_page_count = 0;
839         bp->b_addr = NULL;
840         bp->b_length = numblks;
841         bp->b_io_length = numblks;
842 
843         ASSERT(bp->b_map_count == 1);
844         bp->b_bn = XFS_BUF_DADDR_NULL;
845         bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
846         bp->b_maps[0].bm_len = bp->b_length;
847 }
848 
849 static inline struct page *
850 mem_to_page(
851         void                    *addr)
852 {
853         if ((!is_vmalloc_addr(addr))) {
854                 return virt_to_page(addr);
855         } else {
856                 return vmalloc_to_page(addr);
857         }
858 }
859 
860 int
861 xfs_buf_associate_memory(
862         xfs_buf_t               *bp,
863         void                    *mem,
864         size_t                  len)
865 {
866         int                     rval;
867         int                     i = 0;
868         unsigned long           pageaddr;
869         unsigned long           offset;
870         size_t                  buflen;
871         int                     page_count;
872 
873         pageaddr = (unsigned long)mem & PAGE_MASK;
874         offset = (unsigned long)mem - pageaddr;
875         buflen = PAGE_ALIGN(len + offset);
876         page_count = buflen >> PAGE_SHIFT;
877 
878         /* Free any previous set of page pointers */
879         if (bp->b_pages)
880                 _xfs_buf_free_pages(bp);
881 
882         bp->b_pages = NULL;
883         bp->b_addr = mem;
884 
885         rval = _xfs_buf_get_pages(bp, page_count);
886         if (rval)
887                 return rval;
888 
889         bp->b_offset = offset;
890 
891         for (i = 0; i < bp->b_page_count; i++) {
892                 bp->b_pages[i] = mem_to_page((void *)pageaddr);
893                 pageaddr += PAGE_SIZE;
894         }
895 
896         bp->b_io_length = BTOBB(len);
897         bp->b_length = BTOBB(buflen);
898 
899         return 0;
900 }
901 
902 xfs_buf_t *
903 xfs_buf_get_uncached(
904         struct xfs_buftarg      *target,
905         size_t                  numblks,
906         int                     flags)
907 {
908         unsigned long           page_count;
909         int                     error, i;
910         struct xfs_buf          *bp;
911         DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
912 
913         /* flags might contain irrelevant bits, pass only what we care about */
914         bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
915         if (unlikely(bp == NULL))
916                 goto fail;
917 
918         page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
919         error = _xfs_buf_get_pages(bp, page_count);
920         if (error)
921                 goto fail_free_buf;
922 
923         for (i = 0; i < page_count; i++) {
924                 bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
925                 if (!bp->b_pages[i])
926                         goto fail_free_mem;
927         }
928         bp->b_flags |= _XBF_PAGES;
929 
930         error = _xfs_buf_map_pages(bp, 0);
931         if (unlikely(error)) {
932                 xfs_warn(target->bt_mount,
933                         "%s: failed to map pages", __func__);
934                 goto fail_free_mem;
935         }
936 
937         trace_xfs_buf_get_uncached(bp, _RET_IP_);
938         return bp;
939 
940  fail_free_mem:
941         while (--i >= 0)
942                 __free_page(bp->b_pages[i]);
943         _xfs_buf_free_pages(bp);
944  fail_free_buf:
945         xfs_buf_free_maps(bp);
946         kmem_zone_free(xfs_buf_zone, bp);
947  fail:
948         return NULL;
949 }
950 
951 /*
952  *      Increment reference count on buffer, to hold the buffer concurrently
953  *      with another thread which may release (free) the buffer asynchronously.
954  *      Must hold the buffer already to call this function.
955  */
956 void
957 xfs_buf_hold(
958         xfs_buf_t               *bp)
959 {
960         trace_xfs_buf_hold(bp, _RET_IP_);
961         atomic_inc(&bp->b_hold);
962 }
963 
964 /*
965  * Release a hold on the specified buffer. If the hold count is 1, the buffer is
966  * placed on LRU or freed (depending on b_lru_ref).
967  */
968 void
969 xfs_buf_rele(
970         xfs_buf_t               *bp)
971 {
972         struct xfs_perag        *pag = bp->b_pag;
973         bool                    release;
974         bool                    freebuf = false;
975 
976         trace_xfs_buf_rele(bp, _RET_IP_);
977 
978         if (!pag) {
979                 ASSERT(list_empty(&bp->b_lru));
980                 if (atomic_dec_and_test(&bp->b_hold)) {
981                         xfs_buf_ioacct_dec(bp);
982                         xfs_buf_free(bp);
983                 }
984                 return;
985         }
986 
987         ASSERT(atomic_read(&bp->b_hold) > 0);
988 
989         release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
990         spin_lock(&bp->b_lock);
991         if (!release) {
992                 /*
993                  * Drop the in-flight state if the buffer is already on the LRU
994                  * and it holds the only reference. This is racy because we
995                  * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
996                  * ensures the decrement occurs only once per-buf.
997                  */
998                 if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
999                         __xfs_buf_ioacct_dec(bp);
1000                 goto out_unlock;
1001         }
1002 
1003         /* the last reference has been dropped ... */
1004         __xfs_buf_ioacct_dec(bp);
1005         if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
1006                 /*
1007                  * If the buffer is added to the LRU take a new reference to the
1008                  * buffer for the LRU and clear the (now stale) dispose list
1009                  * state flag
1010                  */
1011                 if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
1012                         bp->b_state &= ~XFS_BSTATE_DISPOSE;
1013                         atomic_inc(&bp->b_hold);
1014                 }
1015                 spin_unlock(&pag->pag_buf_lock);
1016         } else {
1017                 /*
1018                  * most of the time buffers will already be removed from the
1019                  * LRU, so optimise that case by checking for the
1020                  * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
1021                  * was on was the disposal list
1022                  */
1023                 if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
1024                         list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
1025                 } else {
1026                         ASSERT(list_empty(&bp->b_lru));
1027                 }
1028 
1029                 ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1030                 rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
1031                                        xfs_buf_hash_params);
1032                 spin_unlock(&pag->pag_buf_lock);
1033                 xfs_perag_put(pag);
1034                 freebuf = true;
1035         }
1036 
1037 out_unlock:
1038         spin_unlock(&bp->b_lock);
1039 
1040         if (freebuf)
1041                 xfs_buf_free(bp);
1042 }
1043 
1044 
1045 /*
1046  *      Lock a buffer object, if it is not already locked.
1047  *
1048  *      If we come across a stale, pinned, locked buffer, we know that we are
1049  *      being asked to lock a buffer that has been reallocated. Because it is
1050  *      pinned, we know that the log has not been pushed to disk and hence it
1051  *      will still be locked.  Rather than continuing to have trylock attempts
1052  *      fail until someone else pushes the log, push it ourselves before
1053  *      returning.  This means that the xfsaild will not get stuck trying
1054  *      to push on stale inode buffers.
1055  */
1056 int
1057 xfs_buf_trylock(
1058         struct xfs_buf          *bp)
1059 {
1060         int                     locked;
1061 
1062         locked = down_trylock(&bp->b_sema) == 0;
1063         if (locked) {
1064                 XB_SET_OWNER(bp);
1065                 trace_xfs_buf_trylock(bp, _RET_IP_);
1066         } else {
1067                 trace_xfs_buf_trylock_fail(bp, _RET_IP_);
1068         }
1069         return locked;
1070 }
1071 
1072 /*
1073  *      Lock a buffer object.
1074  *
1075  *      If we come across a stale, pinned, locked buffer, we know that we
1076  *      are being asked to lock a buffer that has been reallocated. Because
1077  *      it is pinned, we know that the log has not been pushed to disk and
1078  *      hence it will still be locked. Rather than sleeping until someone
1079  *      else pushes the log, push it ourselves before trying to get the lock.
1080  */
1081 void
1082 xfs_buf_lock(
1083         struct xfs_buf          *bp)
1084 {
1085         trace_xfs_buf_lock(bp, _RET_IP_);
1086 
1087         if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
1088                 xfs_log_force(bp->b_target->bt_mount, 0);
1089         down(&bp->b_sema);
1090         XB_SET_OWNER(bp);
1091 
1092         trace_xfs_buf_lock_done(bp, _RET_IP_);
1093 }
1094 
1095 void
1096 xfs_buf_unlock(
1097         struct xfs_buf          *bp)
1098 {
1099         ASSERT(xfs_buf_islocked(bp));
1100 
1101         XB_CLEAR_OWNER(bp);
1102         up(&bp->b_sema);
1103 
1104         trace_xfs_buf_unlock(bp, _RET_IP_);
1105 }
1106 
1107 STATIC void
1108 xfs_buf_wait_unpin(
1109         xfs_buf_t               *bp)
1110 {
1111         DECLARE_WAITQUEUE       (wait, current);
1112 
1113         if (atomic_read(&bp->b_pin_count) == 0)
1114                 return;
1115 
1116         add_wait_queue(&bp->b_waiters, &wait);
1117         for (;;) {
1118                 set_current_state(TASK_UNINTERRUPTIBLE);
1119                 if (atomic_read(&bp->b_pin_count) == 0)
1120                         break;
1121                 io_schedule();
1122         }
1123         remove_wait_queue(&bp->b_waiters, &wait);
1124         set_current_state(TASK_RUNNING);
1125 }
1126 
1127 /*
1128  *      Buffer Utility Routines
1129  */
1130 
1131 void
1132 xfs_buf_ioend(
1133         struct xfs_buf  *bp)
1134 {
1135         bool            read = bp->b_flags & XBF_READ;
1136 
1137         trace_xfs_buf_iodone(bp, _RET_IP_);
1138 
1139         bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
1140 
1141         /*
1142          * Pull in IO completion errors now. We are guaranteed to be running
1143          * single threaded, so we don't need the lock to read b_io_error.
1144          */
1145         if (!bp->b_error && bp->b_io_error)
1146                 xfs_buf_ioerror(bp, bp->b_io_error);
1147 
1148         /* Only validate buffers that were read without errors */
1149         if (read && !bp->b_error && bp->b_ops) {
1150                 ASSERT(!bp->b_iodone);
1151                 bp->b_ops->verify_read(bp);
1152         }
1153 
1154         if (!bp->b_error)
1155                 bp->b_flags |= XBF_DONE;
1156 
1157         if (bp->b_iodone)
1158                 (*(bp->b_iodone))(bp);
1159         else if (bp->b_flags & XBF_ASYNC)
1160                 xfs_buf_relse(bp);
1161         else
1162                 complete(&bp->b_iowait);
1163 }
1164 
1165 static void
1166 xfs_buf_ioend_work(
1167         struct work_struct      *work)
1168 {
1169         struct xfs_buf          *bp =
1170                 container_of(work, xfs_buf_t, b_ioend_work);
1171 
1172         xfs_buf_ioend(bp);
1173 }
1174 
1175 static void
1176 xfs_buf_ioend_async(
1177         struct xfs_buf  *bp)
1178 {
1179         INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work);
1180         queue_work(bp->b_ioend_wq, &bp->b_ioend_work);
1181 }
1182 
1183 void
1184 __xfs_buf_ioerror(
1185         xfs_buf_t               *bp,
1186         int                     error,
1187         xfs_failaddr_t          failaddr)
1188 {
1189         ASSERT(error <= 0 && error >= -1000);
1190         bp->b_error = error;
1191         trace_xfs_buf_ioerror(bp, error, failaddr);
1192 }
1193 
1194 void
1195 xfs_buf_ioerror_alert(
1196         struct xfs_buf          *bp,
1197         const char              *func)
1198 {
1199         xfs_alert(bp->b_target->bt_mount,
1200 "metadata I/O error in \"%s\" at daddr 0x%llx len %d error %d",
1201                         func, (uint64_t)XFS_BUF_ADDR(bp), bp->b_length,
1202                         -bp->b_error);
1203 }
1204 
1205 int
1206 xfs_bwrite(
1207         struct xfs_buf          *bp)
1208 {
1209         int                     error;
1210 
1211         ASSERT(xfs_buf_islocked(bp));
1212 
1213         bp->b_flags |= XBF_WRITE;
1214         bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
1215                          XBF_WRITE_FAIL | XBF_DONE);
1216 
1217         error = xfs_buf_submit_wait(bp);
1218         if (error) {
1219                 xfs_force_shutdown(bp->b_target->bt_mount,
1220                                    SHUTDOWN_META_IO_ERROR);
1221         }
1222         return error;
1223 }
1224 
1225 static void
1226 xfs_buf_bio_end_io(
1227         struct bio              *bio)
1228 {
1229         struct xfs_buf          *bp = (struct xfs_buf *)bio->bi_private;
1230 
1231         /*
1232          * don't overwrite existing errors - otherwise we can lose errors on
1233          * buffers that require multiple bios to complete.
1234          */
1235         if (bio->bi_status) {
1236                 int error = blk_status_to_errno(bio->bi_status);
1237 
1238                 cmpxchg(&bp->b_io_error, 0, error);
1239         }
1240 
1241         if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1242                 invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1243 
1244         if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1245                 xfs_buf_ioend_async(bp);
1246         bio_put(bio);
1247 }
1248 
1249 static void
1250 xfs_buf_ioapply_map(
1251         struct xfs_buf  *bp,
1252         int             map,
1253         int             *buf_offset,
1254         int             *count,
1255         int             op,
1256         int             op_flags)
1257 {
1258         int             page_index;
1259         int             total_nr_pages = bp->b_page_count;
1260         int             nr_pages;
1261         struct bio      *bio;
1262         sector_t        sector =  bp->b_maps[map].bm_bn;
1263         int             size;
1264         int             offset;
1265 
1266         /* skip the pages in the buffer before the start offset */
1267         page_index = 0;
1268         offset = *buf_offset;
1269         while (offset >= PAGE_SIZE) {
1270                 page_index++;
1271                 offset -= PAGE_SIZE;
1272         }
1273 
1274         /*
1275          * Limit the IO size to the length of the current vector, and update the
1276          * remaining IO count for the next time around.
1277          */
1278         size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1279         *count -= size;
1280         *buf_offset += size;
1281 
1282 next_chunk:
1283         atomic_inc(&bp->b_io_remaining);
1284         nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
1285 
1286         bio = bio_alloc(GFP_NOIO, nr_pages);
1287         bio_set_dev(bio, bp->b_target->bt_bdev);
1288         bio->bi_iter.bi_sector = sector;
1289         bio->bi_end_io = xfs_buf_bio_end_io;
1290         bio->bi_private = bp;
1291         bio_set_op_attrs(bio, op, op_flags);
1292 
1293         for (; size && nr_pages; nr_pages--, page_index++) {
1294                 int     rbytes, nbytes = PAGE_SIZE - offset;
1295 
1296                 if (nbytes > size)
1297                         nbytes = size;
1298 
1299                 rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1300                                       offset);
1301                 if (rbytes < nbytes)
1302                         break;
1303 
1304                 offset = 0;
1305                 sector += BTOBB(nbytes);
1306                 size -= nbytes;
1307                 total_nr_pages--;
1308         }
1309 
1310         if (likely(bio->bi_iter.bi_size)) {
1311                 if (xfs_buf_is_vmapped(bp)) {
1312                         flush_kernel_vmap_range(bp->b_addr,
1313                                                 xfs_buf_vmap_len(bp));
1314                 }
1315                 submit_bio(bio);
1316                 if (size)
1317                         goto next_chunk;
1318         } else {
1319                 /*
1320                  * This is guaranteed not to be the last io reference count
1321                  * because the caller (xfs_buf_submit) holds a count itself.
1322                  */
1323                 atomic_dec(&bp->b_io_remaining);
1324                 xfs_buf_ioerror(bp, -EIO);
1325                 bio_put(bio);
1326         }
1327 
1328 }
1329 
1330 STATIC void
1331 _xfs_buf_ioapply(
1332         struct xfs_buf  *bp)
1333 {
1334         struct blk_plug plug;
1335         int             op;
1336         int             op_flags = 0;
1337         int             offset;
1338         int             size;
1339         int             i;
1340 
1341         /*
1342          * Make sure we capture only current IO errors rather than stale errors
1343          * left over from previous use of the buffer (e.g. failed readahead).
1344          */
1345         bp->b_error = 0;
1346 
1347         /*
1348          * Initialize the I/O completion workqueue if we haven't yet or the
1349          * submitter has not opted to specify a custom one.
1350          */
1351         if (!bp->b_ioend_wq)
1352                 bp->b_ioend_wq = bp->b_target->bt_mount->m_buf_workqueue;
1353 
1354         if (bp->b_flags & XBF_WRITE) {
1355                 op = REQ_OP_WRITE;
1356                 if (bp->b_flags & XBF_SYNCIO)
1357                         op_flags = REQ_SYNC;
1358                 if (bp->b_flags & XBF_FUA)
1359                         op_flags |= REQ_FUA;
1360                 if (bp->b_flags & XBF_FLUSH)
1361                         op_flags |= REQ_PREFLUSH;
1362 
1363                 /*
1364                  * Run the write verifier callback function if it exists. If
1365                  * this function fails it will mark the buffer with an error and
1366                  * the IO should not be dispatched.
1367                  */
1368                 if (bp->b_ops) {
1369                         bp->b_ops->verify_write(bp);
1370                         if (bp->b_error) {
1371                                 xfs_force_shutdown(bp->b_target->bt_mount,
1372                                                    SHUTDOWN_CORRUPT_INCORE);
1373                                 return;
1374                         }
1375                 } else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
1376                         struct xfs_mount *mp = bp->b_target->bt_mount;
1377 
1378                         /*
1379                          * non-crc filesystems don't attach verifiers during
1380                          * log recovery, so don't warn for such filesystems.
1381                          */
1382                         if (xfs_sb_version_hascrc(&mp->m_sb)) {
1383                                 xfs_warn(mp,
1384                                         "%s: no buf ops on daddr 0x%llx len %d",
1385                                         __func__, bp->b_bn, bp->b_length);
1386                                 xfs_hex_dump(bp->b_addr,
1387                                                 XFS_CORRUPTION_DUMP_LEN);
1388                                 dump_stack();
1389                         }
1390                 }
1391         } else if (bp->b_flags & XBF_READ_AHEAD) {
1392                 op = REQ_OP_READ;
1393                 op_flags = REQ_RAHEAD;
1394         } else {
1395                 op = REQ_OP_READ;
1396         }
1397 
1398         /* we only use the buffer cache for meta-data */
1399         op_flags |= REQ_META;
1400 
1401         /*
1402          * Walk all the vectors issuing IO on them. Set up the initial offset
1403          * into the buffer and the desired IO size before we start -
1404          * _xfs_buf_ioapply_vec() will modify them appropriately for each
1405          * subsequent call.
1406          */
1407         offset = bp->b_offset;
1408         size = BBTOB(bp->b_io_length);
1409         blk_start_plug(&plug);
1410         for (i = 0; i < bp->b_map_count; i++) {
1411                 xfs_buf_ioapply_map(bp, i, &offset, &size, op, op_flags);
1412                 if (bp->b_error)
1413                         break;
1414                 if (size <= 0)
1415                         break;  /* all done */
1416         }
1417         blk_finish_plug(&plug);
1418 }
1419 
1420 /*
1421  * Asynchronous IO submission path. This transfers the buffer lock ownership and
1422  * the current reference to the IO. It is not safe to reference the buffer after
1423  * a call to this function unless the caller holds an additional reference
1424  * itself.
1425  */
1426 void
1427 xfs_buf_submit(
1428         struct xfs_buf  *bp)
1429 {
1430         trace_xfs_buf_submit(bp, _RET_IP_);
1431 
1432         ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1433         ASSERT(bp->b_flags & XBF_ASYNC);
1434 
1435         /* on shutdown we stale and complete the buffer immediately */
1436         if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1437                 xfs_buf_ioerror(bp, -EIO);
1438                 bp->b_flags &= ~XBF_DONE;
1439                 xfs_buf_stale(bp);
1440                 xfs_buf_ioend(bp);
1441                 return;
1442         }
1443 
1444         if (bp->b_flags & XBF_WRITE)
1445                 xfs_buf_wait_unpin(bp);
1446 
1447         /* clear the internal error state to avoid spurious errors */
1448         bp->b_io_error = 0;
1449 
1450         /*
1451          * The caller's reference is released during I/O completion.
1452          * This occurs some time after the last b_io_remaining reference is
1453          * released, so after we drop our Io reference we have to have some
1454          * other reference to ensure the buffer doesn't go away from underneath
1455          * us. Take a direct reference to ensure we have safe access to the
1456          * buffer until we are finished with it.
1457          */
1458         xfs_buf_hold(bp);
1459 
1460         /*
1461          * Set the count to 1 initially, this will stop an I/O completion
1462          * callout which happens before we have started all the I/O from calling
1463          * xfs_buf_ioend too early.
1464          */
1465         atomic_set(&bp->b_io_remaining, 1);
1466         xfs_buf_ioacct_inc(bp);
1467         _xfs_buf_ioapply(bp);
1468 
1469         /*
1470          * If _xfs_buf_ioapply failed, we can get back here with only the IO
1471          * reference we took above. If we drop it to zero, run completion so
1472          * that we don't return to the caller with completion still pending.
1473          */
1474         if (atomic_dec_and_test(&bp->b_io_remaining) == 1) {
1475                 if (bp->b_error)
1476                         xfs_buf_ioend(bp);
1477                 else
1478                         xfs_buf_ioend_async(bp);
1479         }
1480 
1481         xfs_buf_rele(bp);
1482         /* Note: it is not safe to reference bp now we've dropped our ref */
1483 }
1484 
1485 /*
1486  * Synchronous buffer IO submission path, read or write.
1487  */
1488 int
1489 xfs_buf_submit_wait(
1490         struct xfs_buf  *bp)
1491 {
1492         int             error;
1493 
1494         trace_xfs_buf_submit_wait(bp, _RET_IP_);
1495 
1496         ASSERT(!(bp->b_flags & (_XBF_DELWRI_Q | XBF_ASYNC)));
1497 
1498         if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1499                 xfs_buf_ioerror(bp, -EIO);
1500                 xfs_buf_stale(bp);
1501                 bp->b_flags &= ~XBF_DONE;
1502                 return -EIO;
1503         }
1504 
1505         if (bp->b_flags & XBF_WRITE)
1506                 xfs_buf_wait_unpin(bp);
1507 
1508         /* clear the internal error state to avoid spurious errors */
1509         bp->b_io_error = 0;
1510 
1511         /*
1512          * For synchronous IO, the IO does not inherit the submitters reference
1513          * count, nor the buffer lock. Hence we cannot release the reference we
1514          * are about to take until we've waited for all IO completion to occur,
1515          * including any xfs_buf_ioend_async() work that may be pending.
1516          */
1517         xfs_buf_hold(bp);
1518 
1519         /*
1520          * Set the count to 1 initially, this will stop an I/O completion
1521          * callout which happens before we have started all the I/O from calling
1522          * xfs_buf_ioend too early.
1523          */
1524         atomic_set(&bp->b_io_remaining, 1);
1525         _xfs_buf_ioapply(bp);
1526 
1527         /*
1528          * make sure we run completion synchronously if it raced with us and is
1529          * already complete.
1530          */
1531         if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1532                 xfs_buf_ioend(bp);
1533 
1534         /* wait for completion before gathering the error from the buffer */
1535         trace_xfs_buf_iowait(bp, _RET_IP_);
1536         wait_for_completion(&bp->b_iowait);
1537         trace_xfs_buf_iowait_done(bp, _RET_IP_);
1538         error = bp->b_error;
1539 
1540         /*
1541          * all done now, we can release the hold that keeps the buffer
1542          * referenced for the entire IO.
1543          */
1544         xfs_buf_rele(bp);
1545         return error;
1546 }
1547 
1548 void *
1549 xfs_buf_offset(
1550         struct xfs_buf          *bp,
1551         size_t                  offset)
1552 {
1553         struct page             *page;
1554 
1555         if (bp->b_addr)
1556                 return bp->b_addr + offset;
1557 
1558         offset += bp->b_offset;
1559         page = bp->b_pages[offset >> PAGE_SHIFT];
1560         return page_address(page) + (offset & (PAGE_SIZE-1));
1561 }
1562 
1563 /*
1564  *      Move data into or out of a buffer.
1565  */
1566 void
1567 xfs_buf_iomove(
1568         xfs_buf_t               *bp,    /* buffer to process            */
1569         size_t                  boff,   /* starting buffer offset       */
1570         size_t                  bsize,  /* length to copy               */
1571         void                    *data,  /* data address                 */
1572         xfs_buf_rw_t            mode)   /* read/write/zero flag         */
1573 {
1574         size_t                  bend;
1575 
1576         bend = boff + bsize;
1577         while (boff < bend) {
1578                 struct page     *page;
1579                 int             page_index, page_offset, csize;
1580 
1581                 page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1582                 page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1583                 page = bp->b_pages[page_index];
1584                 csize = min_t(size_t, PAGE_SIZE - page_offset,
1585                                       BBTOB(bp->b_io_length) - boff);
1586 
1587                 ASSERT((csize + page_offset) <= PAGE_SIZE);
1588 
1589                 switch (mode) {
1590                 case XBRW_ZERO:
1591                         memset(page_address(page) + page_offset, 0, csize);
1592                         break;
1593                 case XBRW_READ:
1594                         memcpy(data, page_address(page) + page_offset, csize);
1595                         break;
1596                 case XBRW_WRITE:
1597                         memcpy(page_address(page) + page_offset, data, csize);
1598                 }
1599 
1600                 boff += csize;
1601                 data += csize;
1602         }
1603 }
1604 
1605 /*
1606  *      Handling of buffer targets (buftargs).
1607  */
1608 
1609 /*
1610  * Wait for any bufs with callbacks that have been submitted but have not yet
1611  * returned. These buffers will have an elevated hold count, so wait on those
1612  * while freeing all the buffers only held by the LRU.
1613  */
1614 static enum lru_status
1615 xfs_buftarg_wait_rele(
1616         struct list_head        *item,
1617         struct list_lru_one     *lru,
1618         spinlock_t              *lru_lock,
1619         void                    *arg)
1620 
1621 {
1622         struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1623         struct list_head        *dispose = arg;
1624 
1625         if (atomic_read(&bp->b_hold) > 1) {
1626                 /* need to wait, so skip it this pass */
1627                 trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
1628                 return LRU_SKIP;
1629         }
1630         if (!spin_trylock(&bp->b_lock))
1631                 return LRU_SKIP;
1632 
1633         /*
1634          * clear the LRU reference count so the buffer doesn't get
1635          * ignored in xfs_buf_rele().
1636          */
1637         atomic_set(&bp->b_lru_ref, 0);
1638         bp->b_state |= XFS_BSTATE_DISPOSE;
1639         list_lru_isolate_move(lru, item, dispose);
1640         spin_unlock(&bp->b_lock);
1641         return LRU_REMOVED;
1642 }
1643 
1644 void
1645 xfs_wait_buftarg(
1646         struct xfs_buftarg      *btp)
1647 {
1648         LIST_HEAD(dispose);
1649         int loop = 0;
1650 
1651         /*
1652          * First wait on the buftarg I/O count for all in-flight buffers to be
1653          * released. This is critical as new buffers do not make the LRU until
1654          * they are released.
1655          *
1656          * Next, flush the buffer workqueue to ensure all completion processing
1657          * has finished. Just waiting on buffer locks is not sufficient for
1658          * async IO as the reference count held over IO is not released until
1659          * after the buffer lock is dropped. Hence we need to ensure here that
1660          * all reference counts have been dropped before we start walking the
1661          * LRU list.
1662          */
1663         while (percpu_counter_sum(&btp->bt_io_count))
1664                 delay(100);
1665         flush_workqueue(btp->bt_mount->m_buf_workqueue);
1666 
1667         /* loop until there is nothing left on the lru list. */
1668         while (list_lru_count(&btp->bt_lru)) {
1669                 list_lru_walk(&btp->bt_lru, xfs_buftarg_wait_rele,
1670                               &dispose, LONG_MAX);
1671 
1672                 while (!list_empty(&dispose)) {
1673                         struct xfs_buf *bp;
1674                         bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1675                         list_del_init(&bp->b_lru);
1676                         if (bp->b_flags & XBF_WRITE_FAIL) {
1677                                 xfs_alert(btp->bt_mount,
1678 "Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
1679                                         (long long)bp->b_bn);
1680                                 xfs_alert(btp->bt_mount,
1681 "Please run xfs_repair to determine the extent of the problem.");
1682                         }
1683                         xfs_buf_rele(bp);
1684                 }
1685                 if (loop++ != 0)
1686                         delay(100);
1687         }
1688 }
1689 
1690 static enum lru_status
1691 xfs_buftarg_isolate(
1692         struct list_head        *item,
1693         struct list_lru_one     *lru,
1694         spinlock_t              *lru_lock,
1695         void                    *arg)
1696 {
1697         struct xfs_buf          *bp = container_of(item, struct xfs_buf, b_lru);
1698         struct list_head        *dispose = arg;
1699 
1700         /*
1701          * we are inverting the lru lock/bp->b_lock here, so use a trylock.
1702          * If we fail to get the lock, just skip it.
1703          */
1704         if (!spin_trylock(&bp->b_lock))
1705                 return LRU_SKIP;
1706         /*
1707          * Decrement the b_lru_ref count unless the value is already
1708          * zero. If the value is already zero, we need to reclaim the
1709          * buffer, otherwise it gets another trip through the LRU.
1710          */
1711         if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1712                 spin_unlock(&bp->b_lock);
1713                 return LRU_ROTATE;
1714         }
1715 
1716         bp->b_state |= XFS_BSTATE_DISPOSE;
1717         list_lru_isolate_move(lru, item, dispose);
1718         spin_unlock(&bp->b_lock);
1719         return LRU_REMOVED;
1720 }
1721 
1722 static unsigned long
1723 xfs_buftarg_shrink_scan(
1724         struct shrinker         *shrink,
1725         struct shrink_control   *sc)
1726 {
1727         struct xfs_buftarg      *btp = container_of(shrink,
1728                                         struct xfs_buftarg, bt_shrinker);
1729         LIST_HEAD(dispose);
1730         unsigned long           freed;
1731 
1732         freed = list_lru_shrink_walk(&btp->bt_lru, sc,
1733                                      xfs_buftarg_isolate, &dispose);
1734 
1735         while (!list_empty(&dispose)) {
1736                 struct xfs_buf *bp;
1737                 bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1738                 list_del_init(&bp->b_lru);
1739                 xfs_buf_rele(bp);
1740         }
1741 
1742         return freed;
1743 }
1744 
1745 static unsigned long
1746 xfs_buftarg_shrink_count(
1747         struct shrinker         *shrink,
1748         struct shrink_control   *sc)
1749 {
1750         struct xfs_buftarg      *btp = container_of(shrink,
1751                                         struct xfs_buftarg, bt_shrinker);
1752         return list_lru_shrink_count(&btp->bt_lru, sc);
1753 }
1754 
1755 void
1756 xfs_free_buftarg(
1757         struct xfs_mount        *mp,
1758         struct xfs_buftarg      *btp)
1759 {
1760         unregister_shrinker(&btp->bt_shrinker);
1761         ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
1762         percpu_counter_destroy(&btp->bt_io_count);
1763         list_lru_destroy(&btp->bt_lru);
1764 
1765         xfs_blkdev_issue_flush(btp);
1766 
1767         kmem_free(btp);
1768 }
1769 
1770 int
1771 xfs_setsize_buftarg(
1772         xfs_buftarg_t           *btp,
1773         unsigned int            sectorsize)
1774 {
1775         /* Set up metadata sector size info */
1776         btp->bt_meta_sectorsize = sectorsize;
1777         btp->bt_meta_sectormask = sectorsize - 1;
1778 
1779         if (set_blocksize(btp->bt_bdev, sectorsize)) {
1780                 xfs_warn(btp->bt_mount,
1781                         "Cannot set_blocksize to %u on device %pg",
1782                         sectorsize, btp->bt_bdev);
1783                 return -EINVAL;
1784         }
1785 
1786         /* Set up device logical sector size mask */
1787         btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
1788         btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
1789 
1790         return 0;
1791 }
1792 
1793 /*
1794  * When allocating the initial buffer target we have not yet
1795  * read in the superblock, so don't know what sized sectors
1796  * are being used at this early stage.  Play safe.
1797  */
1798 STATIC int
1799 xfs_setsize_buftarg_early(
1800         xfs_buftarg_t           *btp,
1801         struct block_device     *bdev)
1802 {
1803         return xfs_setsize_buftarg(btp, bdev_logical_block_size(bdev));
1804 }
1805 
1806 xfs_buftarg_t *
1807 xfs_alloc_buftarg(
1808         struct xfs_mount        *mp,
1809         struct block_device     *bdev,
1810         struct dax_device       *dax_dev)
1811 {
1812         xfs_buftarg_t           *btp;
1813 
1814         btp = kmem_zalloc(sizeof(*btp), KM_SLEEP | KM_NOFS);
1815 
1816         btp->bt_mount = mp;
1817         btp->bt_dev =  bdev->bd_dev;
1818         btp->bt_bdev = bdev;
1819         btp->bt_daxdev = dax_dev;
1820 
1821         if (xfs_setsize_buftarg_early(btp, bdev))
1822                 goto error_free;
1823 
1824         if (list_lru_init(&btp->bt_lru))
1825                 goto error_free;
1826 
1827         if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
1828                 goto error_lru;
1829 
1830         btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
1831         btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
1832         btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1833         btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
1834         if (register_shrinker(&btp->bt_shrinker))
1835                 goto error_pcpu;
1836         return btp;
1837 
1838 error_pcpu:
1839         percpu_counter_destroy(&btp->bt_io_count);
1840 error_lru:
1841         list_lru_destroy(&btp->bt_lru);
1842 error_free:
1843         kmem_free(btp);
1844         return NULL;
1845 }
1846 
1847 /*
1848  * Cancel a delayed write list.
1849  *
1850  * Remove each buffer from the list, clear the delwri queue flag and drop the
1851  * associated buffer reference.
1852  */
1853 void
1854 xfs_buf_delwri_cancel(
1855         struct list_head        *list)
1856 {
1857         struct xfs_buf          *bp;
1858 
1859         while (!list_empty(list)) {
1860                 bp = list_first_entry(list, struct xfs_buf, b_list);
1861 
1862                 xfs_buf_lock(bp);
1863                 bp->b_flags &= ~_XBF_DELWRI_Q;
1864                 list_del_init(&bp->b_list);
1865                 xfs_buf_relse(bp);
1866         }
1867 }
1868 
1869 /*
1870  * Add a buffer to the delayed write list.
1871  *
1872  * This queues a buffer for writeout if it hasn't already been.  Note that
1873  * neither this routine nor the buffer list submission functions perform
1874  * any internal synchronization.  It is expected that the lists are thread-local
1875  * to the callers.
1876  *
1877  * Returns true if we queued up the buffer, or false if it already had
1878  * been on the buffer list.
1879  */
1880 bool
1881 xfs_buf_delwri_queue(
1882         struct xfs_buf          *bp,
1883         struct list_head        *list)
1884 {
1885         ASSERT(xfs_buf_islocked(bp));
1886         ASSERT(!(bp->b_flags & XBF_READ));
1887 
1888         /*
1889          * If the buffer is already marked delwri it already is queued up
1890          * by someone else for imediate writeout.  Just ignore it in that
1891          * case.
1892          */
1893         if (bp->b_flags & _XBF_DELWRI_Q) {
1894                 trace_xfs_buf_delwri_queued(bp, _RET_IP_);
1895                 return false;
1896         }
1897 
1898         trace_xfs_buf_delwri_queue(bp, _RET_IP_);
1899 
1900         /*
1901          * If a buffer gets written out synchronously or marked stale while it
1902          * is on a delwri list we lazily remove it. To do this, the other party
1903          * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
1904          * It remains referenced and on the list.  In a rare corner case it
1905          * might get readded to a delwri list after the synchronous writeout, in
1906          * which case we need just need to re-add the flag here.
1907          */
1908         bp->b_flags |= _XBF_DELWRI_Q;
1909         if (list_empty(&bp->b_list)) {
1910                 atomic_inc(&bp->b_hold);
1911                 list_add_tail(&bp->b_list, list);
1912         }
1913 
1914         return true;
1915 }
1916 
1917 /*
1918  * Compare function is more complex than it needs to be because
1919  * the return value is only 32 bits and we are doing comparisons
1920  * on 64 bit values
1921  */
1922 static int
1923 xfs_buf_cmp(
1924         void            *priv,
1925         struct list_head *a,
1926         struct list_head *b)
1927 {
1928         struct xfs_buf  *ap = container_of(a, struct xfs_buf, b_list);
1929         struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
1930         xfs_daddr_t             diff;
1931 
1932         diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
1933         if (diff < 0)
1934                 return -1;
1935         if (diff > 0)
1936                 return 1;
1937         return 0;
1938 }
1939 
1940 /*
1941  * submit buffers for write.
1942  *
1943  * When we have a large buffer list, we do not want to hold all the buffers
1944  * locked while we block on the request queue waiting for IO dispatch. To avoid
1945  * this problem, we lock and submit buffers in groups of 50, thereby minimising
1946  * the lock hold times for lists which may contain thousands of objects.
1947  *
1948  * To do this, we sort the buffer list before we walk the list to lock and
1949  * submit buffers, and we plug and unplug around each group of buffers we
1950  * submit.
1951  */
1952 static int
1953 xfs_buf_delwri_submit_buffers(
1954         struct list_head        *buffer_list,
1955         struct list_head        *wait_list)
1956 {
1957         struct xfs_buf          *bp, *n;
1958         LIST_HEAD               (submit_list);
1959         int                     pinned = 0;
1960         struct blk_plug         plug;
1961 
1962         list_sort(NULL, buffer_list, xfs_buf_cmp);
1963 
1964         blk_start_plug(&plug);
1965         list_for_each_entry_safe(bp, n, buffer_list, b_list) {
1966                 if (!wait_list) {
1967                         if (xfs_buf_ispinned(bp)) {
1968                                 pinned++;
1969                                 continue;
1970                         }
1971                         if (!xfs_buf_trylock(bp))
1972                                 continue;
1973                 } else {
1974                         xfs_buf_lock(bp);
1975                 }
1976 
1977                 /*
1978                  * Someone else might have written the buffer synchronously or
1979                  * marked it stale in the meantime.  In that case only the
1980                  * _XBF_DELWRI_Q flag got cleared, and we have to drop the
1981                  * reference and remove it from the list here.
1982                  */
1983                 if (!(bp->b_flags & _XBF_DELWRI_Q)) {
1984                         list_del_init(&bp->b_list);
1985                         xfs_buf_relse(bp);
1986                         continue;
1987                 }
1988 
1989                 trace_xfs_buf_delwri_split(bp, _RET_IP_);
1990 
1991                 /*
1992                  * We do all IO submission async. This means if we need
1993                  * to wait for IO completion we need to take an extra
1994                  * reference so the buffer is still valid on the other
1995                  * side. We need to move the buffer onto the io_list
1996                  * at this point so the caller can still access it.
1997                  */
1998                 bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_WRITE_FAIL);
1999                 bp->b_flags |= XBF_WRITE | XBF_ASYNC;
2000                 if (wait_list) {
2001                         xfs_buf_hold(bp);
2002                         list_move_tail(&bp->b_list, wait_list);
2003                 } else
2004                         list_del_init(&bp->b_list);
2005 
2006                 xfs_buf_submit(bp);
2007         }
2008         blk_finish_plug(&plug);
2009 
2010         return pinned;
2011 }
2012 
2013 /*
2014  * Write out a buffer list asynchronously.
2015  *
2016  * This will take the @buffer_list, write all non-locked and non-pinned buffers
2017  * out and not wait for I/O completion on any of the buffers.  This interface
2018  * is only safely useable for callers that can track I/O completion by higher
2019  * level means, e.g. AIL pushing as the @buffer_list is consumed in this
2020  * function.
2021  */
2022 int
2023 xfs_buf_delwri_submit_nowait(
2024         struct list_head        *buffer_list)
2025 {
2026         return xfs_buf_delwri_submit_buffers(buffer_list, NULL);
2027 }
2028 
2029 /*
2030  * Write out a buffer list synchronously.
2031  *
2032  * This will take the @buffer_list, write all buffers out and wait for I/O
2033  * completion on all of the buffers. @buffer_list is consumed by the function,
2034  * so callers must have some other way of tracking buffers if they require such
2035  * functionality.
2036  */
2037 int
2038 xfs_buf_delwri_submit(
2039         struct list_head        *buffer_list)
2040 {
2041         LIST_HEAD               (wait_list);
2042         int                     error = 0, error2;
2043         struct xfs_buf          *bp;
2044 
2045         xfs_buf_delwri_submit_buffers(buffer_list, &wait_list);
2046 
2047         /* Wait for IO to complete. */
2048         while (!list_empty(&wait_list)) {
2049                 bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
2050 
2051                 list_del_init(&bp->b_list);
2052 
2053                 /* locking the buffer will wait for async IO completion. */
2054                 xfs_buf_lock(bp);
2055                 error2 = bp->b_error;
2056                 xfs_buf_relse(bp);
2057                 if (!error)
2058                         error = error2;
2059         }
2060 
2061         return error;
2062 }
2063 
2064 /*
2065  * Push a single buffer on a delwri queue.
2066  *
2067  * The purpose of this function is to submit a single buffer of a delwri queue
2068  * and return with the buffer still on the original queue. The waiting delwri
2069  * buffer submission infrastructure guarantees transfer of the delwri queue
2070  * buffer reference to a temporary wait list. We reuse this infrastructure to
2071  * transfer the buffer back to the original queue.
2072  *
2073  * Note the buffer transitions from the queued state, to the submitted and wait
2074  * listed state and back to the queued state during this call. The buffer
2075  * locking and queue management logic between _delwri_pushbuf() and
2076  * _delwri_queue() guarantee that the buffer cannot be queued to another list
2077  * before returning.
2078  */
2079 int
2080 xfs_buf_delwri_pushbuf(
2081         struct xfs_buf          *bp,
2082         struct list_head        *buffer_list)
2083 {
2084         LIST_HEAD               (submit_list);
2085         int                     error;
2086 
2087         ASSERT(bp->b_flags & _XBF_DELWRI_Q);
2088 
2089         trace_xfs_buf_delwri_pushbuf(bp, _RET_IP_);
2090 
2091         /*
2092          * Isolate the buffer to a new local list so we can submit it for I/O
2093          * independently from the rest of the original list.
2094          */
2095         xfs_buf_lock(bp);
2096         list_move(&bp->b_list, &submit_list);
2097         xfs_buf_unlock(bp);
2098 
2099         /*
2100          * Delwri submission clears the DELWRI_Q buffer flag and returns with
2101          * the buffer on the wait list with an associated reference. Rather than
2102          * bounce the buffer from a local wait list back to the original list
2103          * after I/O completion, reuse the original list as the wait list.
2104          */
2105         xfs_buf_delwri_submit_buffers(&submit_list, buffer_list);
2106 
2107         /*
2108          * The buffer is now under I/O and wait listed as during typical delwri
2109          * submission. Lock the buffer to wait for I/O completion. Rather than
2110          * remove the buffer from the wait list and release the reference, we
2111          * want to return with the buffer queued to the original list. The
2112          * buffer already sits on the original list with a wait list reference,
2113          * however. If we let the queue inherit that wait list reference, all we
2114          * need to do is reset the DELWRI_Q flag.
2115          */
2116         xfs_buf_lock(bp);
2117         error = bp->b_error;
2118         bp->b_flags |= _XBF_DELWRI_Q;
2119         xfs_buf_unlock(bp);
2120 
2121         return error;
2122 }
2123 
2124 int __init
2125 xfs_buf_init(void)
2126 {
2127         xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
2128                                                 KM_ZONE_HWALIGN, NULL);
2129         if (!xfs_buf_zone)
2130                 goto out;
2131 
2132         return 0;
2133 
2134  out:
2135         return -ENOMEM;
2136 }
2137 
2138 void
2139 xfs_buf_terminate(void)
2140 {
2141         kmem_zone_destroy(xfs_buf_zone);
2142 }
2143 
2144 void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
2145 {
2146         /*
2147          * Set the lru reference count to 0 based on the error injection tag.
2148          * This allows userspace to disrupt buffer caching for debug/testing
2149          * purposes.
2150          */
2151         if (XFS_TEST_ERROR(false, bp->b_target->bt_mount,
2152                            XFS_ERRTAG_BUF_LRU_REF))
2153                 lru_ref = 0;
2154 
2155         atomic_set(&bp->b_lru_ref, lru_ref);
2156 }
2157 

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